Brown leaf spot of poplar

Brown leaf spot of poplar is a widespread fungal disease caused by the ascomycete fungus Drepanopeziza populi (anamorph stage: Marssonina populi). This pathogen specifically targets the foliage of various poplar species, significantly impacting the tree's vitality and photosynthetic capacity during the active growing season.

The disease primarily affects different species of poplars, particularly in nurseries and plantations where humidity levels are high. Susceptibility varies greatly between clones, making the selection of resistant varieties a key component of integrated pest management for commercial timber and urban landscaping.

Symptoms initially appear as small, circular or irregular spots on the leaves, which are brown to reddish-brown in color. As the infection progresses, these spots expand, often merging into larger necrotic areas. Small, light-colored or black fruiting bodies develop on the spots, releasing spores that can cause secondary infections throughout the summer.

Environmental conditions play a critical role in the development and spread of the disease. Prolonged wet weather, high humidity, and moderate temperatures provide the perfect environment for spore production and dispersal. The pathogen overwinters in the fallen leaves, which serve as the primary source of inoculum for new infections in the following spring.

Effective management strategies for brown leaf spot involve a combination of cultural and chemical practices to minimize damage. Key protective measures include:

• Removal and destruction of fallen leaves in late autumn to reduce overwintering sites;
• Planting resistant or tolerant poplar cultivars;
• Applying fungicides during the early stages of disease development;
• Maintaining proper tree spacing to improve air circulation and reduce humidity levels.